In the electrical energy conveyance art there is often a need to use existing inaccessible electrical wiring in order to achieve some new and originally unconsidered function. A “smart” ability to accomplish this new function can often save significant amounts of work and expense involved in a rework effort. This set of events is encountered in a plurality of differing applications of the electrical arts, i.e., in numerous fields of endeavor including buildings and transportation equipment of differing types.
One example of this situation is to be found in the electrical wiring of certain rooms in many homes especially in the United States but also other locations of the world. In these rooms, such as in a bedroom, there is originally provided a ceiling light fixture controlled by a wall mounted light switch located near the entrance door of the room. Energy for lighting the lamp of this fixture may be supplied to either of a small metal electrical box containing the wall switch or to the small metal electrical box used to mount the light fixture in the room ceiling. In either event the original house wiring often includes a single pair of lamp fixture controlling electrical conductors running between the two metal boxes, conductors that are buried and securely attached to structural members of the house before a wall covering such as plaster board or wet plaster is put in place. Such conductors are of course later inaccessible for enhancements such as an increase in conductor numbers without substantial destructive and reconstruction efforts. Local building codes in a few locations of the U.S. provide an exception to this general rule in requiring the use of “conduit” or pipe-like pathways and pulled-in conductors between these metal boxes and thus allow for new conductor retrofitting when needed. Communities around the city of Chicago, Ill. are for example known to have such local code rules. In most locations however original wiring is of the “Romex” or “BX” or even older “knob and tube” varieties and is thus rigidly attached to or passing through structural members of the house and is now inaccessible.
A problem with this usual wiring arrangement often arises when a new or additional usage of one or more of these boxes is contemplated, a use such as providing a combination electrical light and ceiling fan is desired in the room. When the box to box conductors are two in number, lie buried between wall surfaces and between first floor ceiling and second floor flooring and consist of flexible “Romex” or “BX” or other common two conductor residential wiring forms, the provision of a new third or additional electrical conductors for separate control of fan speed, fan direction and lamp intensities for example is a significant dilemma.
One clever solution to this electrical art dilemma has been provided by the Casablanca Fan Company located in California, USA. Combination fan and light fixtures provided by this supplier do in fact provide a plurality of differing fan speeds and directions and lamp illumination intensities all with use of only the two original conductors joining the ceiling and wall boxes! The Casablanca designers have accomplished this plurality of control functions through use of control signals coded into the sinusoid waveform of the supplied electrical energy wave. The Casablanca coding is embedded in the controlled energy wave near the sinusoid waveform zero voltage crossing points. Such coding is accomplished with wave slicing events performed by bidirectional semiconductor devices of the silicon controlled rectifier type, devices known in the art as “thyristors” or by other names proprietary to the device supplier. A more complete description of the Casablanca control is provided in a series of U.S. Patents including U.S. Pat. No. 4,716,409 issued to Casablanca designers, this and any other patent identified in this document are hereby incorporated by reference herein.
Although the Casablanca control and coding technique is elegant in design and performance it is limited by practicalities such as nearby lightning surges being often destructive of semiconductor devices when integrated into long house wiring runs, by switch contact resistance increasing over use lifetime, by generation of distorted sinusoid wave shapes (that are minimally diminished in electrical energy delivery effect but include high frequency harmonics, a possible source of radio frequency interference noise) and by the inherent applicability of the coding only to alternating current electrical energy sources. Generally it also may be stated that the Casablanca coding intentionally distorts an incoming sinusoidal wave in order to introduce the control coding as opposed to adding additional sinusoids to an incoming waveform in order to embed the control signals. The zero crossing coding of the Casablanca technique may nevertheless generally be considered as one clever and practical approach to communicating control signals by way of two energy delivery conductors and to the use of limited conductor existing wiring for new and more demanding applications.
As described herein there is additional need for arrangements somewhat of this nature in electrical applications outside of the house and building environment. It is for example particularly difficult to re-wire an aircraft in order to provide for new exterior or interior light sources or to energize other loads especially when such loads may necessitate physical dispositions at distant locations of a large airframe and thus require transmission of energy through hundreds of feet of integrally assembled and hidden factory installed wiring. Re wiring is of further increased difficulty when the wiring in an originally installed factory bundle is now characterized by electrical insulation degradation such as embrittlement or chafing or where the aircraft includes decorative or thermal insulation interior panels or other physical obstructions for examples. One needs only to consider the conclusions reached with respect to TWA flight 800 in New York to appreciate the significance of fragility in existing aircraft wiring. Aircraft rewiring is in fact so difficult and costly that the practice of “retirement in place” for original wiring has become commonplace in older aircraft, particularly in military aircraft.
In the art of improving existing aircraft with upgraded electronic systems, as has been practiced in several cycles in for example the fleet of B-52 bombers used by the U.S. Air Force since the mid 1950's, it may be convenient to reuse the electrical conductors of a somewhat large-conductor factory-wired bus of significant length and advantageous physical location for certain new equipment not in existence at the time of original aircraft fabrication. For example electronic equipment at the time of B-52 design was almost totally dependent on vacuum tubes and thus was characterized by low input to output efficiency, larger physical size and greater energy usage than is now experienced with integrated circuits and other semiconductor equipment. In a related manner smart missile weapons and global position system equipment for examples were completely unknown at the time of B-52 design but now are necessary additions for effective present day usage of such aircraft.
Similar examples involving the retrofitting of other aircraft are under current military consideration. The C-130 transport aircraft has been manufactured in several versions for years and certain of these versions are being considered for receipt of enhanced avionics equipment including cockpit displays and controls. Similarly the close ground support fighter aircraft commonly known as the A-10 and “warthog” has been in use for years and has also received modern equipment upgrades. The addition of night vision equipment and the provision of night vision equipment-compatible lighting both inside and outside the aircraft are additional areas of significant present military concern and are believed assisted by the present invention.
The present invention has been found especially useful in the modernization of tanker aircraft wherein both a replacement for incandescent filament lamps with light emitting diode elements and bus signal decoding electronics can all reside in the space reserved for original incandescent lamp fixtures. In such aircraft there exists, for example, a large number of light fixtures used in guiding an aircraft being refueled into correct position for engagement with the refueling boom. These fixtures are used under nighttime conditions and in both friendly and hostile airspace. Some of these guidance lamps now need to house covert or night vision related infrared characteristics in order to provide aircraft safety in hostile airspace. The present invention adds the capability to select between these multiple forms of signal illumination without need to provide additional lamp fixture wiring and other costly and time-consuming changes.
By way of capabilities achieved in the present invention an earlier provided electrical bus, as for old and now removed electronic equipment for example in an aircraft, may be re used to energize several present day loads while the application of energy to these loads is nevertheless individually controlled from the cockpit or from some other point of the aircraft, such as an operator station. Such technique may of course also be applied to newly installed wiring and equipment where it is desirable to reduce conductor numbers, weight or bundle size. According to this arrangement, a single electrical bus may be used to control a plurality of differing loads through signal coding communicated along the same bus conveying the controlled energy. For simplification purposes herein these multiple electrical loads may be represented by light sources of different character located throughout the aircraft and its exterior. Such light sources are of course also possible actual loads that may be energized in this manner, all as described subsequently below herein.